FFmpeg does not require special installation. Just place *.dll files in the folder of your application, or in any folder included in the PATH environment variable.
When uninstalling your application, simply delete these files.

The version of FFmpeg above is rather old.
While the version above is ok for playing video, it offers a small count of codecs for encoding (and some of them were experimental).
I suggest taking newer version of FFmpeg from https://ffmpeg.zeranoe.com/builds/ (RVMedia 5.3 or newer is required to use the newest version of FFmpeg 4; choose the "Shared" option); or create your own build of FFmpeg.